vppn/node/router.go

package node

import (
	"encoding/json"
	"io"
	"log"
	"net/http"
	"net/netip"
	"net/url"
	"sync/atomic"
	"time"
	"vppn/m"
)

var zeroAddrPort = netip.AddrPort{}

type peer struct {
	IP            byte           // The VPN IP.
	Up            bool           // No data will be sent to peers that are down.
	Addr          netip.AddrPort // If we have direct connection, otherwise use mediator.
	Mediator      bool           // True if the peer will mediate.
	RoutingCipher controlCipher
	DataCipher    dataCipher

	// TODO: Deprecated below.
	Mediated  bool
	SharedKey []byte
}

// ----------------------------------------------------------------------------

type routingTable struct {
	table    [256]*atomic.Pointer[peer]
	mediator *atomic.Pointer[peer]
}

func newRoutingTable() *routingTable {
	r := routingTable{
		mediator: &atomic.Pointer[peer]{},
	}

	for i := range r.table {
		r.table[i] = &atomic.Pointer[peer]{}
	}

	return &r
}

func (r *routingTable) Get(ip byte) *peer {
	return r.table[ip].Load()
}

func (r *routingTable) Set(ip byte, p *peer) {
	r.table[ip].Store(p)
}

func (r *routingTable) Mediator() *peer {
	return r.mediator.Load()
}

// ----------------------------------------------------------------------------

type router struct {
	*routingTable
	netName    string
	peerSupers [256]*peerSupervisor
}

func newRouter(netName string, conf m.PeerConfig, routingData *routingTable, w *connWriter) *router {
	r := &router{
		netName:      netName,
		routingTable: routingData,
	}

	for i := range r.peerSupers {
		r.peerSupers[i] = newPeerSupervisor(
			conf,
			byte(i),
			w,
			r.routingTable)
	}

	go r.selectMediator()
	go r.pollHub(conf)

	return r
}

// ----------------------------------------------------------------------------

func (r *router) HandlePacket(sourceIP byte, remoteAddr netip.AddrPort, data []byte) {
	p := routingPacket{}
	if err := p.Parse(data); err != nil {
		log.Printf("Dropping malformed routing packet: %v", err)
		return
	}

	w := routingPacketWrapper{
		routingPacket: p,
		Addr:          remoteAddr,
	}

	r.peerSupers[sourceIP].HandlePacket(w)
}

// ----------------------------------------------------------------------------

func (r *router) pollHub(conf m.PeerConfig) {
	defer panicHandler()

	u, err := url.Parse(conf.HubAddress)
	if err != nil {
		log.Fatalf("Failed to parse hub address %s: %v", conf.HubAddress, err)
	}
	u.Path = "/peer/fetch-state/"

	client := &http.Client{Timeout: 8 * time.Second}

	req := &http.Request{
		Method: http.MethodGet,
		URL:    u,
		Header: http.Header{},
	}
	req.SetBasicAuth("", conf.APIKey)

	state, err := loadNetworkState(r.netName)
	if err != nil {
		log.Printf("Failed to load network state: %v", err)
		log.Printf("Polling hub...")
		r._pollHub(conf, client, req)
	} else {
		r.applyNetworkState(conf, state)
	}

	for range time.Tick(64 * time.Second) {
		r._pollHub(conf, client, req)
	}
}

func (r *router) _pollHub(conf m.PeerConfig, client *http.Client, req *http.Request) {
	var state m.NetworkState

	log.Printf("Fetching peer state from %s...", conf.HubAddress)
	resp, err := client.Do(req)
	if err != nil {
		log.Printf("Failed to fetch peer state: %v", err)
		return
	}
	body, err := io.ReadAll(resp.Body)
	_ = resp.Body.Close()
	if err != nil {
		log.Printf("Failed to read body from hub: %v", err)
		return
	}

	if err := json.Unmarshal(body, &state); err != nil {
		log.Printf("Failed to unmarshal response from hub: %v", err)
		return
	}

	r.applyNetworkState(conf, state)

	if err := storeNetworkState(r.netName, state); err != nil {
		log.Printf("Failed to store network state: %v", err)
	}
}

func (r *router) applyNetworkState(conf m.PeerConfig, state m.NetworkState) {
	for i := range state.Peers {
		if i != int(conf.PeerIP) {
			r.peerSupers[i].HandlePeerUpdate(state.Peers[i])
		}
	}
}

// ----------------------------------------------------------------------------

func (r *router) selectMediator() {
	for range time.Tick(8 * time.Second) {
		current := r.mediator.Load()
		if current != nil && current.Up {
			continue
		}

		for i := range r.table {
			peer := r.table[i].Load()
			if peer != nil && peer.Up && peer.Mediator {
				log.Printf("Got mediator: %v", *peer)
				r.mediator.Store(peer)
				return
			}
		}

		r.mediator.Store(nil)
	}
}